High-frequency coupling circuit



Feb. 25, 1947.

W. M. KELLOGG HIGH FREQUENCY COUPLING CIRCUIT Original Filed Dec. 11, 1941 2 Sheets-Sheet 1 INVENTOR By W. M. KELLOGG Arron/v5 Feb. 25, 1947. WMMKELLOGG 2,416,322

HIGH FREQUENCY COUPLING CIRCUIT Y Original Filed Dec. 11. 1941 2 Sheets-Sheet 2 FIG/0i FIG. 6 A a FIG. 9

1","l'l'l'lll'll'lll will 0 0 g o 43 a 46 5 47 5 0 5 g a/ O 44 2 O I 32 5 0 Z I 57 t I 5 1 o o I z 5 INVENTOR By W M. KELLOGG zromvsv pliflers and the like. v h

This application is a division if my application,

Patented Feb. 25, 1941 wear? 7 I t I WilliamM. Kellogg, Morrlstown, N- J., assignor. to-Bell Telephone Laboratories, Incorporated,

v New Yorln N. Y.,a corporation oi New York.

a Original application December 11, 1941, ScrialNo'.

422,510. Divided and this application October 21. 1942, Serial No. 463,419 Y a a This invention relates to systems and circuits tori providing impedance matching; and tu in at ultra-high radio frequencies and particularly to tuning and impedance matching systems for am- Serial'No. 422,510, filed December 11, 1941. An object of the invention is to provide, an ampliiler' for ultra-high .irequency radio oscillations thatis simple in construction and readily adjustable for operation at different frequencies.

A further object or the invention is to provide a'selective coupling system for ultra-high irequencies.

In 'theoperation of amplifiers and similar circults in the ultra-high. frequency range, it has been found that circuits having distributed condrawing in 'which:

stants are superiorto lumped constant circuits for use for tuning,,impedancematching', neutralizing and the like. For'example, one method of tuning the input of ,an amplifier and matching its impedance to the incoming us connectto the amplifierlinput a, short-circuited section 01' -transmission line the length of which. is so ad:

justed that'in combination with the input impedance of the amplifier it acts as a quarter wave-length line at theirequencyotthewaves to be amplified. Withsuch arrangementthe i o line may be ta ped onto the short circuited line at a. point where the two, impedances are equal. Electrically; such a system operates very-satisfactorily. Also where the amplifier is g to be used only at a single frequency .the apparatus can be quite readily" constructed and adiusted iorsuch satisfactory operation. However, where the system'isto be adjustable to;permit operation at any of anu nber of frequencies,

' there are certain structural diiliculties. Among these isthe problem of providing {or thevariable connection between the incoming line and the quarter wave' line particularly sinceflexible lines arenot entirely satisfactory for waves in the ultra-high frequencyrange.

I In accordance with aifeatureof the present inventionthere is provided a system in which .the

incoming line is connected enemy to the amplifler input and there is further provided a stub line or adjustable length which may be connected to the incoming line at'various points along the' ingcondenser 34.

. l1 is provided to tune the input circuit andprovide proper impedance matching forthe input. 3 V

system is the electrical equivalent of thesystem frequencies. -for coupling to the input of anamplifier but also.

by reference to the following detaileddescriptlon of one embodiment of the invention in an'ult'ra Fig. 4 is amendflvie'w partly in section}; Q

line' II, Fig. 5 beinglan endelevat'ion and of which is illustrated. in the other figures. This g amplifler comprises a triode vacuumtuber! I m I closed in ashield comprising a portionlilfsur-h rounding the tube itselt'and a sectionportion QII conductor or sheath l4 anda tubularinnercon-E' 45' the shield 12 and connected tothe' cathodeoithe tube H through the direct current blocking conplanation thoughin the actual construction or just described andat the same time is re adily capable of, adjustment for operation atdiilerent Such systems are not only suitable for output and interstage coupling. This invention can be morereadily understood high'radio rrequencyamplii'ler as shown the Fig. i is a schematic circuit diagram hereufl T Fig.2isaplanview; a H

Fig. 3 is a fr i'it elevation, partly.

n i I Figs. 5' and 5A are detailed views oithef 5 aside elevation: 1 V 1 Fig, 6 is a detailed plan ,viewtiin enlarg scale) taken along the line 66 of Fig.

.. "Fig. '7' is a detailed front elevationoi the-per tionshowninFighfi; 5 Fig.1}; is a detailed .end elevation ta enalong 3 I the, line 8,--8 of Fig. 6 andjshowing the construc-v tion' otgth'e filament -bypas's condensers; 1

Fig. 9.15 a detailed inverted plan YlEWZOffihe filament by-pass condensers; and. l

Fig. 1 0 is adetailed explodedview oi the Fig.1 shows in a somewhatco ventionalschematic circuit form the ultra-high i'requency anig plifler ofgthe present invention, the construction closing the top of the tube shield andvals'oen closing the neutralizing line, to be described later. The radio frequency I input'to th tub'e is brought in through a concentric line comprisln'gfan outer ductor l5. Theouter. conductor is grounded v.to

densers l6 and 26. IA short-circuited"stub. line 1 i T e stubline comprises an outer conductorjor shield l1, an inner conductor l8 j and a shortrcircuiting member l9. (Thislatter' member. II'is shown adjustable in Fig. lior purposes of ex- 1 the .othenfigures itisfixedlthus mung thelength; The shield l1 contacts :the

voi! the stub line.)

outerconductor or thefinput'line and the inner 1 conductor 18 contactsthe fthe inputline. V

a The jstub line 11 is;movable' along the input line so that the'length ofthe'short-circuited secinner conductor I5 .01 j

tion from the grid or tube II to the shorting amember lillmay be adjusted. This provides -.,a; tuningrsection vbetween the grid connection and I the shorts-circuited'terminal' whicnwhen adjust-' ed to the equivalent quarter wave-length 'oiythe resonant. line section :at the junction of the line v Il -l5 and the. stub :line 11. .By adJustingtheL- reactance of the stub line I], i. e., its length is input oscillations in ei fect tunes the-amplifier in- 1 put-circuit. At. the same time the input portion} oflthe line ll-l 5is in .efiect tapped intosthis determined by the position of the shorting mem-l 5 her [9; it .is also possible toobtain a proper impedance match for the emcient The equivalent'electrical circuit, that is 'aqua rter wave-length line for tuning with an intermemamas-m 'impedance matching, is familiar to those skilled in the, art-." I -Iowever, "applicant's 1 structure avoids a "serious'i handicapof the previ- I ous arrangements in which itwas'necessary. in 1 FDR-Q61; to make the impedance matching adjustment to useza flexible section "of incoming'iine. Such an arrangem ent is undesirable, particularly Y whenoperating in the higher frequen'cy ranges.

conductor 25 anda'shortingimember' 29. The

used ,forinterstage couplingihWhich case itleads lar manner 'tothe in'putli'ne lfll 5.

its inductance can be adjustedltogive a reac'tance neutraiizingthe effect of the latter.

7 The adjustment may also be made to cause the amplifier to; operate as .a regenerative amplifier, j Serif-desired; p v t termination or v The plate or output circuit or the amplifier-is sinned and 'emcie'ntly coupled to the outgoing -co 1 I axial line'24'- bya'similar arrangement. This 1 comprises the coaxial line having an innertubu- -lar conductor '24 connectedat the'innerend to the plate of the tube ll throughza ,blo'ckingvcondenser; and ,an outer conductor 25 connected to the grounded, shield 1 2:1" The blocking condensers, l6 and 26 serve :to connect the cathode of tube H. ,T e adjustablestub line 21, which is similarto the 'line I1,fisl'alsbprovide;1 and 'comprisesa shild'fl'contactingthe outer conductor 24, an inner conductor v2 8 contacting the inner direct current plate supply is'b'rought'in through v the insulated wire 30; earrie,d within the tubular V inneuconductor 25.1 The line :'2425 may be I to a secondxamplifler-and is terminated in a simiz a 'The tub llmis'neutralizedt 'prevent thegeni V jerati'on ofspuriousosciilationsbyf'meansofythe balanced line 31-32. 'One'side 3| of this line is "connect'edto thegrid of tube H, The other'side is"- connected' to the plate of tube 11 l thlfbughi the 1 blocking'condenser 34 ."TheQ-line"3l+32f-'is.,adjustably short-circuited b'y themeniber 33 so that eq'uai'to thatofthe 'grid-toplate capacity,"thus 1 izing rods 3l circuits. l p v lheampllfierisf Sj upported'inainly bytheIhousring is andis morefclearlyshown.inl igsi 6 to.9.

Theinput concentric line comprising the'sheath )M and the :inner conductor l.5.is supp0rted..in the right -wall' ofjthe housing l3.;jFor thispuron the end (of h clam i v bracket :41 andthe plateterrninal socket 48. The neutralizing jrod '3l is carried by .thefibracketj'l. 76

The line 3l-325is enclosed inzthe-"shieldillj 'Each side of'theline 31-732 acts ,asvthe centerconductorof an approximately concentric lineof which the cylindrical shield l3is the sheath.v This-v presents-an impedance from the plateand from the igridjto'jthe sheath l3 that. is {determined .by the characteristic impedancandlength of these concentric lines. Thelengthis determined by the shorting member 33 which isextended to contact vthe sheath I3. ,Since thelcathode and sheath-are at substantially the same radio frequency potential the grid and plate circuits are additionally tuned bythis system. vTherefore,

theseconcentric lines should be self-resonant or have suificient inductive reactance topartialiyor wholly, resonatezthe grid-sheath and plate-sheath capacitances" with the shorting member 33in the, position that permitsthebalanced line 3l32 to tune the grid-plate capacitance vto resonance. These; requirements placea restriction on the diyameters Offth neutralizing r'ods 3| and 32 and the inner diameter'yof the *sheath or'shield I3.

- It is preferable that there be approximate equality-of the-characteristic impedance'of the rods as a balanced line or as individualIunbalanced (concentric) linesp Accordingly, at any setting Q of the member 331essthan-a quarter wave-length a triangle ofapproximatelyequal inductive re- 'acta'nce is presented tothe tube-ll. Thispro- 'vides the-'reactances desired for a'tubesuch as V the ,Western Electric 703A vacuum tube, the interelectrode -capacitancesof'which' are approximately equal. 'For a tube of difierent character istics, 'difierent line parameters would be" pre-' ferrd; I v a v v In neutralizing. the amplifier, the plate voltageis removed and witha highsignal input the in "put and output stub lines I! andgil are set for maximum output whilethe member 33 is adjusted for Y the: (maximum; ratio of, input, to output. When'. so neutralized,"the input and output circuits can'be retunedyindependentl y-birga' read- For the actual' structure of l a practicallembodimentof my invention reference is made to Figs.-

2' to e lo ofithe drawing in which. the 3 same mer- 7 ence numerals are ,usedthroughout for like e1e-' 'ment's. Referring'flrst toiFigs. 2, and 3, the am-' plifierlis built on a "panel or base-40; Above; this base andsecured thereto by screws is-a shielding c easin -la, This shield 13 is made squarein cross sectionifor mechanical reasons but is the substantial electrical equivalent of j a circular shield-vasregardsits cooperation with the neutralpose the inner. endg ll is, turneddownforminga v reduced portion and iashouider which is mounted in-aholej in thewall- 421w a press fit. A discin I sulator 43' is mounted ,in' a" recess ;in;the.' inner end .of the sheath, l4 ,b'ymeans ofLa. spr'ingretaining ring 4.4. The inner hollow tubularconduc'tor l 5fisv'mounted in' a centrally locatedehole in the dis'c143 an'disecuredthereby. the nut 45. Ciamped I the conductor- 15 is a clamping block. i.

block] dii vfcarrie's "on l". shaped I Theipl'ate circuit'concentricline, zlzs ssmand'32 intuning the gridand plate ilarly mounted in a second hole in the will I. An insulated wire 38 forming the direct current connection to the plate is run'through the hollow inner conductor 28. Thewire 38 is brought out of the conductor 28 at a point of low radio frequency impedance as shown in Fig. 3 thus simplifying the filtering of the direct current circuit. A clamping block 88 is mounted on the inner end of the conductor 28. Like the block 48, this block 88' carries a neutralizing rod 32 and the socket 58 for the plate terminal of the tube I I. However, the socket I8 is directly mounted in block 48, while terminal 88 is mounted in the block 58 through the medium of an insulating bushing to form the blocking condenser 34. Fig; 10 shows this construction.

I atlases v make contact with the shaft 88 is journaled in this block 85 and carries two pinionsf81 and 88 within the shield I3 and a knurled knob 89 outside. The pinions 81 and". i

mesh with the teeth of the respective racks 9 8 and Referring to Fig. 10, which is an exploded view of the condenser 34, the socket." is screwed onto the threaded end of rod 88. The other end 8| is of reduced size forming a soldering terminal for the direct current lead 38. A bushing 82 fits over the intermediate portion of the rod 88. This bushing 82 is of a lava type insulating material clamped in a split portlonof the block 88 means of the screw 84. A similar construction is used for clamping the block to the conductor l8.

An assembly of cathode circuit condensers I8 and 28 is also mounted in theshield I3. These comprise a mounting plate I8 screwed to angles 89 suitably mounted on the inner walls of the shield l3. Two irregularly shaped plates 'II and -I2 are screwed to the plate I8 and separated therefrom by the sheet of mica I3. Insulating washers I4 prevent the screw heads from making electrical contact with plates II and I2. 801- dering terminals II. and l2.I are provided on the plates II and I respectively, for connecting the leads which furnish heating current to the cathode of the tube II. Cathode terminal sockets I8 and It for the tube II are mounted on plates II and I2 respectively.

The tube I I is mounted below the panel 48, being supported from the sockets 48, 88, I8 and II by its electrode terminals. The shield I2 surrounds the tube I I and is provided with a removable cover I2.I for access to the tube.

The short-circuit member 33 is mounted in the the ' shield I3. This is provided with a wiper 82 which contacts the rod 32. A similar wiper, not visible in the drawing, contacts the rod 3|. The'plate member 33 is also provided with brushes 83 which SI secured to the inside of the shield I3. Thus by turning the knob 89 the position of theplate 33 and consequently the effective length of the balanced neutralizing line and the, unbalanced plate and gridilines may be' adjusted. A pointer 92. and scale 83 give an indication of the adjust ment.-.

Figs. 5 and stubline II, the stub line 21 being identical thereto. This comprises an outer housing or shield I88] formed largely of sheet metal but having two solid end blocks I8I soldered to the sheet metal portion'. The lower end' of each of these end blocks 7' IN is machined to form a tongue I82, which rides I in the slotv J inthe top of the outer conductor Riding on the inside of the conductor I8 is a shoe I83'that is fastened to the end blocks I 8| by means of the machine screws I88 and springs I88. A wiper 188 contacts the inner conductor 3 I8. This wiper; is carried by a stem I8 forming I the inner conductor of the stub line H. The, stem I8 is carried by two guide blocks I 81 to which it is riveted. The assembly of blocks I81 and stem I8 are secured to the casing I08 by means of machine screws I88. and I89. The screw I89in ad dition carries a strip II8 thelower end of which is bent outwardly and pointed to form an indicator III. This indicator cooperates with the scale H2 toindicate the adjustment of the stub lines I1 and 21.

What is claimed is: r 'In a high frequency system, a concentric line comprising an outer tubular conductor slotted for a portion of its length near one end and an inner conductor mounted within said outer conductor,

an electric discharge amplifier connected to said line at said one end, and a stub line comprising an outer rectangular shield having a shoulder portion adapted to ride in the slot of said outer" tubular conductor, a guide member riding within said outer tubular conductor and resiliently attached to said outer shield, an inner conductor mounted within said outer shield and conductively supported thereby at one end and a wiper connected to said inner conductor at the other end and riding on the inner conductor of said concentric line.

r WILLIAM M. KELLOGG.

, REFERENCES CITED The following references are oi record the.

file of this patent: v

UNITED STATES PATENTS Number Name Date i 2,019,809 Carter Nov.'5, 193,5 2.213,0 54 Schussler Aug. 27, 1940 inner surface of the shield I3. A block 88 is. attached to the plate 33. .A

5A show the construction ofth'e, I 

